SOUTH LAKE TAHOE, CA

HISTORY OF THE SIERRA NEVADA'S

BY SANDRA CHURCHILL

Table of Contents

• Dandelions: pages…….. 3,4

• Pine Trees: pages……… 5,6

• Brewers Blackbird: pages…….. 7,8

• Granite: pages……….. 9,10

• Scoria Rock page……… 11

• Rhyolite Rock page………. 12

• Cross-cutting relationships pages…. 13-17

• Angular Unconformity…….. 18

• Principle of inclusion…….. 19

• References……. 20,21

DANDELION – FRENCH DENT DE LION

• From the Devonian period about 385-359 MYA. (Willis, McElwain)

• Dandelions are, quite possibly, the most successful plants that exist, masters of survival, worldwide.

• They are the oldest of flowers dating back to early the Egyptians. (Hanrahan)

• If you mow dandelions, they’ll grow shorter stalks to spite you.

• They do not need pollination. That means if you have one in your yard over time you could have millions. ( Hanrahan)

YOU PROBABLY SAYING TO YOURSELF " I HOPE THAT IS NOT HER HOME!"AND I'M SAYING "I HOPE THAT THIS IS NOT YOUR HOME!"THE TRUTH IS THAT DANDELIONS CAN OVERTAKE ANY HOME GARDEN IF LEFT NOT TREATED. THEY ARE MASTERS OF EVOLUTION.

LODGE POLE PINE TREE- PINUS CONTORTA GINKGO - CLOSEST LIVING RELATIVE TO GYMNOSPERMSo ALL PINE TREES CAME FROM GYMNOSPERMS FROM THE TRIASSIC PERIOD 200-250 MYA.o THE LODGE POLE PINE IS A RESILIENT TREE THAT ADAPTS WELL TO DROUGHT CONDITIONSo LODGEPOLE PINE GROWS ON SOILS THAT VARY WIDELY BUT ARE USUALLY MOIST. GROWTH IS BEST WHERE SOIL

PARENT MATERIALS ARE GRANITES, SHALES, AND COARSE-GRAINED LAVAS (DESPAIN)o THE 3–7 CM CONES OFTEN NEED EXPOSURE TO HIGH TEMPERATURES (SUCH AS FROM FOREST FIRES) IN ORDER TO

OPEN AND RELEASE THEIR SEED (FEDUCK)

FOSSIL AND 3 OTHER PINE TREES FOUND IN LAKE TAHOE BASIN

PONDEROSA PINE SUGAR PINE WHITE FUR140 MYO TREE BRANCH

BREWERS BLACKBIRD

From the Cenozoic period 65-0 MYA Brewer’s Blackbirds are social birds that nest in

colonies of up to 100 birds. (Martin, Stephen G. 2002)

Brewer’s Blackbirds are quick to notice new food sources and have been credited with helping to curb outbreaks of insect pests

I have seen that they protect their young by swooping down at the back of the head of humans or animals that get close. When they swoop, they get really close!

PICTURE OF NEST WAS TAKEN IN MY BACK YARD-SOUTH LAKE TAHOE, CA

We also note that many all-black species of blackbirds nest in open habitats that are not marshes (e.g., Brewer's blackbird in savannas. Thus, it seems unlikely that openness of habitat per se is a major factor driving the evolution of plumage patches in marsh-nesting blackbirds (Orians, 1985). The female is the one that makes the nest out of small sticks

and other material found close. I risked my life to get this picture!

THE FIRST PICTURE BELOW IS ONE OF GRANITE THAT WAS CHIPPED TO FORM RECTANGULAR BLOCKS THAT CAN BE USED FOR RETAINING WALLS AND LANDSCAPE DECORATION

ALL GRANITE EXPOSED ON THE SURFACE OF THE EARTH HAD TO BE UPLIFTED FROM DEPTH, USUALLY FROM ABOUT ONE TO 20 MILES DOWN.

GRANITE IS RADIOACTIVE. LIKE MANY OTHER NATURAL MATERIALS, IT CONTAINS TRACE AMOUNTS OF URANIUM. SOME GRANITE BODIES, HOWEVER, CAN HAVE 5 TO 20 TIMES THE NORMAL AMOUNT OF URANIUM, THE BYPRODUCT OF WHICH IS RADON GAS, WHICH HAS BEEN SHOWN TO CAUSE LUNG CANCER

PINK GRANITES OWE THEIR COLOR TO RED OR PINK ALKALI FELDSPARSTHE SIERRA NEVADA MOUNTAINS ARE ABUNDANT IN GRANITE ROCK FORMATIONS30 MILLION YEARS AGO, DURING AN EPISODE GEOLOGISTS CALL A MAGMATIC FLARE-UP. DURING

THIS TIME, AN OCEANIC PLATE THAT HAD BEEN SLIDING UNDERNEATH NORTH AMERICA BROKE APART, EXPOSING THE BOTTOM OF THE NORTH AMERICAN CONTINENTAL PLATE TO HOT MANTLE ROCKS. THIS HEATING CREATED NEW POCKETS OF MAGMA, AND EVENTUALLY BODIES OF GRANITE CALLED PLUTONS ACROSS THE AMERICAN WEST. (ALLEN)

GRANITE BOLDER-IGNEOUS ROCK

HALF DOME-YOSEMITE NATIONAL PARK

SCORIA IS A DARK-COLORED IGNEOUS ROCK WITH ABUNDANT ROUND BUBBLE-LIKE CAVITIES KNOWN AS VESICLES. IT RANGES IN COLOR FROM BLACK OR DARK GRAY TO DEEP REDDISH BROWN. SCORIA

USUALLY HAS A COMPOSITION SIMILAR TO BASALT, BUT IT CAN ALSO HAVE A COMPOSITION SIMILAR TO ANDESITE. (MCPHEE, DOYLE, ALLEN)

MANY PEOPLE BELIEVE THAT SMALL PIECES OF SCORIA LOOK LIKE THE ASH PRODUCED IN A COAL FURNACE. THAT HAS RESULTED IN

PARTICLES OF SCORIA BEING CALLED "CINDERS" AND THE SMALL VOLCANOES THAT ERUPT SCORIA TO BE CALLED "CINDER CONES."

Scoria- Igneous Rock

RHYOLITE-IGNEOUS ROCKFOUND IN MY FRONT YARD WHEN A TREE STUMP WAS REMOVED . NOW USED IN MY LANDSCAPE

RHYOLITE WITH MULTIPLE VUGS FILLED WITH GEMMY TRANSPARENT ORANGE FIRE OPAL.

Trapped gases often produce vugs in the rock.

CROSS-CUTTING RELATIONSHIPS

LAKE TAHOE IN THE SIERRA NEVADA'S

ABOUT 400 MILLION YEARS AGO WHEN WHAT IS NOW THE SIERRA

NEVADA’S WAS COMPLETELY COVERED WITH SEA WATER, THE SEA

FLOOR WAS MADE UP OF MUD, SAND, AND SHELLS. THIS MATERIAL

CONTINUED TO BUILD UP ON THE SEA FLOOR. AFTER A FEW

MILLION YEARS THE WEIGHT OF THE SEDIMENT, ALONG WITH SOME

CHEMICALS PROCESSING TURNED THOSE SEDIMENTS INTO A

COMBINATION OF MUDSTONE, AND SANDSTONE . THEN THE

PACIFIC PLATE AND THE NORTH AMERICAN PLATE COLLIDED

CAUSING WHAT IS KNOWN AS SUBDUCTION. SUBDUCTION IS

WHEN ONE PLATE IS PUSHED DOWNWARD BENEATH ANOTHER

PLATE INTO THE UNDERLYING MANTLE WHEN PLATES MOVE

TOWARDS EACH OTHER.(GARDNER, MAYER HUGHES)

THREE MAJOR FAULTS ARE WHAT CREATED LAKE TAHOE BASIN.

AFTER THE FAULTS MADE THE SIERRA

NEVADA MOUNTAIN

RANGE, THEN…

THE ICE AGE ALONG WITH GLACIERS FINISHED THE REST.

THESE TWO IMAGES SHOW HOW GLACIER MOVEMENT BROUGHT THE GRANITE MOUNTAINS INTO THE

BASIN OF THE LAKE

THEN THE MELTING OF THE GLACIER FILLED THE LAKE. THERE IS ONLY ONE OUTLET IN LAKE TAHOE, THE

TRUCKEE RIVER.

ANGULAR UNCONFORMITYTHESE ARE FORMED FROM UPHEAVALS THAT TILT THE LOWER ROCKS AND FORM MOUNTAINS THAT WERE THEN WORN AWAY AND COVERED BY YOUNGER, FLAT-LAYING ROCKS.(MONROE AND WICANDER)

PRINCIPLE OF INCLUSION

THIS IS THE SAME PICTURE FROM THE SLIDE BEFORE

THIS TIME WE ARE LOOKING AT THE PRINCIPLE OF INCLUSION (SORRY DON'T HAVE A CLOSE UP).

IN IT YOU CAN SEE THE SMALL BOULDERS THAT ARE TRAPPED FROM THE VOLCANIC ERUPTION THAT OCCURRED MILLIONS OF TEARS AGO. THE TRAPPED BOULDERS HAD TO HAVE EXISTED BEFORE THE ERUPTION BECAUSE THEY ARE NOW TRAPPED IN THE ROCK LAYERS.

THIS IS THE PRINCIPLE OF INCLUSION.

Martin, Stephen G. 2002. Brewer's Blackbird (Euphagus cyanocephalus). In The Birds of North America, No. 616 (A. Poole, Ed.). The Birds of North America Online, Ithaca, New York.Orians G, 1985. Blackbirds of the Americas. Seattle: University of Washington Press.

Nancy Kelly Allen, 2009. Granite and other igneous rocks, New York, New York Photo page 4 https://tipsfromashton.wordpress.com/2012/03/25/kill-weeds-without-killing-your-good-grass/

Feduck, Mike, 2015, "The genetic basis of cone serotiny in Pinus contorta as a function of mixed-severity and stand-replacement fire regimes".

Despain, Don G. 1973. Vegetation of the Big Horn Mountains, Wyoming, in relation to substrate and climate. Ecological Monographs 43(3):329-355.Gardner, J., Mayer, L., & Hughes-Clark, J. (1998, August 2-17). The bathymetry of lake tahoe, california-nevada.

Photos on page: 16 ahttp://skywalker.cochise.edu/wellerr/students/lake-tahoe/project.htmPhotos on page 17 http://skywalker.cochise.edu/wellerr/students/lake-tahoe/project.htm

Photo pages11,12 http://geology.com/rocks/scoria.shtml

McPhie, J., M. Doyle, and R. Allen (1993) Volcanic Textures A guide to the interpretation of textures in volcanic rocks Centre for Ore Deposit and Exploration Studies, University of Tasmania, Hobart, Tasmania..198 pp. ISBN 9780859015226

Photo on page 6 http://www.bbc.com/news/science-environment-35767640

K.J.Willis and J.C. McElwain 2002, Evolution of Plants, Oxford University PressJames S. Monroe and Reed Wicander, 2012, The Changing Earth, seventh edition, Stamford, CT.